The invention relates to a combustion engine having at least one cylinder having at least one gas exchange inlet valve and at least one gas exchange outlet valve, and a fuel injection device for injecting fuel directly into the cylinder.
As regards the technical context, attention is drawn to German Laid-Open Application DE 40 416 28 A1, for example. From this document, a mixture-compressing combustion engine with secondary air injection and with air mass measurement is known. This engine also has an injection valve with sequential fuel injection and air assistance, wherein an air line provided for the air assistance is provided with a shutoff valve that opens in the starting and warm-up phase of the combustion engine. With this combustion engine, the fuel injection takes place in the inlet duct in the cylinder head. With this configuration, mixture preparation is improved in the starting and warm-up phase of the combustion engine so as to reduce toxic exhaust gas components.
A system for compensating the boost pressure in pressure-charged internal combustion engines is furthermore known from German Laid-Open Application DE 199 44 946 A1. This system is used to supply turbocharged internal combustion engines with compressed air in order to improve operating behavior outside the optimum operating range of the turbocharger. The system preferably includes a pressure reservoir, a compressor and a valve. The pressure reservoir is supplied continuously with compressed air. If the boost pressure supplied by the turbocharger is not sufficient, the valve is opened and the compressed air is fed from the reservoir into the cylinder for combustion. The purpose of such a system is especially to charge turbocharged internal combustion engines outside the optimum operating range of the turbocharger.
The disadvantage with this configuration is the very high outlay of the apparatus.
A reciprocating-piston combustion engine having at least two inlet valves and associated inlet ducts per cylinder is furthermore known from German Patent DE 40 27 963 C1, wherein the first inlet duct is connected to an exhaust gas recirculation system and the second inlet duct has a fresh-gas turbulence system. The reciprocating-piston combustion engine is characterized in that the exhaust gas recirculation system and the fresh-gas turbulence system are designed as ducts which open with an equal eccentricity into the respective inlet duct in order to generate a swirling flow in the cylinder.
This configuration is used to achieve the object of further increasing the turbulence which arises in the cylinders of a combustion engine of the type in question.
The disadvantage with this known turbulence system is that the turbulence system does not operate in combination with an exhaust turbocharger system owing to the prevailing pressure conditions.
Another system for increasing the turbulence in the combustion chamber of an internal combustion engine while simultaneously providing turbocharging is known from German Patent DE 102 24 719 B4. This patent discloses a device for feeding cylinders of pressure-charged internal combustion engines having the following structure:                a charger is arranged ahead of the intake tract of the internal combustion engine,        a pressure accumulator is connected to the charger with valves controlled by an engine control unit arranged in between in order to fill the intake tract,        from the intake tract, intake pipes, which are each routed to an intake duct of a cylinder, are connected to the cylinder head,        a control flow duct that can be opened in a controlled manner issues ahead of an inlet valve of each cylinder, said duct being connected to the pressure accumulator with a first control valve in between, and        the control valve is controlled electrically in a synchronized manner, directly or indirectly, by the engine control unit during the filling of the respective cylinder.        
With this known device for increasing the turbulence in the combustion chamber of an internal combustion engine, the high outlay of the apparatus is also disadvantageous.
Gas-kinetic injection for pressure charging and introducing water in internal combustion engines is furthermore known from German Laid-Open Application DE 196 17 781 A1. In this laid-open application, there is a proposal to accelerate the air column in the intake pipe at the correct point in time with a small quantity of high-pressure gas (10 to 200 bar) in order to fill or to scavenge the combustion chamber.
The disadvantage with this proposal is the still immense expenditure of air required to accelerate the air column in the intake pipe, while effective influence on the increase in the degree of turbulence in the combustion chamber is still not achieved.
It is the object of the present invention to provide as simple a way as possible of increasing the charge movement (degree of turbulence) in a direct-injection Otto-cycle combustion engine in a simple manner.
This and other objects are achieved by a combustion engine having at least one cylinder having at least one gas exchange inlet valve and at least one gas exchange outlet valve, a fuel injection device for injecting fuel directly into the cylinder, a fresh air section, which can be connected intermittently for gas transmission to the cylinder via the gas exchange inlet valve, and an exhaust section, which can be connected intermittently for gas transmission to the cylinder via the gas exchange outlet valve. A throttle element is provided in the fresh air section ahead of the gas exchange inlet valve in the direction of flow of a fresh air. A fresh gas line line is provided, which opens into the fresh air section after the throttle element, in the region of the at least one gas exchange inlet valve. The fresh gas opens into the fresh air section via a nozzle, which has flow according to Bernoulli, Venturi or Coanda.
By means of a separate duct (fresh gas line), taken to a point ahead of the at least one gas exchange inlet valve, and of a nozzle shaped in accordance with the invention at the end (also referred to as a pulse nozzle, having a flow geometry in accordance with Bernoulli, Venturi or Coanda), it is possible to induce a directional fresh gas pulse into the combustion chamber when the inlet valve is open. Depending on the intensity of this pulse, different levels of charge movement can be produced. The intensity of the fresh gas pulse can be controlled or set in a simple manner by way of a compressor or of a pressure reservoir, which is filled with fresh air or from the fresh gas section with a feed point ahead of the throttle element, for example. In addition to the ignition angle, boost pressure, injection quantity and injection time, the further variable “charge movement” is advantageously available as a result for the application of the combustion engine. Another significant power boost for the combustion engine is possible with the arrangement of a vortex tube in the fresh gas line since a significantly higher filling ratio of the at least one cylinder is possible through the cooling of the fresh air delivered.
Bernoulli:
Bernoulli discovered the relationship between the speed of flow of a fluid and its pressure. He discovered that an increase in speed in a flowing fluid (gas or liquid) is accompanied by a drop in pressure.
The use of “Bernoulli flow” is often found, for example:                in a waterjet pump;        in an intake funnel of a carburetor;        in a Prandtl pitot tube, which is used to measure the speed of an aircraft, for example;        in the flow around the wings of aircraft up to speeds of about 300 km/h.        
Venturi:
The Italian Venturi discovered that the speed of flow of an incompressible fluid flowing through a tube is inversely proportional to the variation in the tube cross section. That is to say that the speed of the fluid is greatest where the cross section of the tube is smallest.
According to the law of continuity for incompressible fluids, the quantity of fluid emerging from any tube section is the same as that introduced into it. The fluid must therefore pass through the constriction at the same flow rate (quantity/time) as the rest of the tube. Therefore, the speed of the fluid must necessarily increase.
Coanda:
The Coanda effect is a collective term used for various phenomena with unrelated causes, referring to the tendency of a gas jet or a liquid flow to “cling” to a convex surface instead of separating from it and moving onward in the original direction of flow.
An accurate definition and a precise distinction from the Bernoulli effect are difficult.
In 1910, Coanda built an airplane, the Coanda-1910. It was to be driven by a combination of a piston-driven compressor and two combustion chambers. The engine was mounted on the tip of the fuselage and exhausted the two thrust jets obliquely rearward. Coanda realized that the exhaust gases were following the contour of the fuselage and flowing along it (Coanda effect), destroying the aircraft.
There are now technical applications of the Coanda effect, e.g. in aeronautics and Formula 1 (exhaust engineering).
Vortex Tube:
The widely known vortex tube is a device by which gas can be divided into a hot stream and a cold stream.
Air under pressure (fresh gas) is injected tangentially into a vortex chamber, being made to rotate rapidly in the process (over 1,000,000 rpm), and leaves the chamber through two different axial air outlets arranged opposite one another:                cooled air emerges through a small hole;        hot air emerges through a significantly larger hole situated opposite.        
The temperature difference between the holes can be up to 46° C., depending on the operating parameters. During this process, there is a whistling sound of about 3 kHz, but this can be attenuated by suitable known measures (although resonators are not suitable for this purpose).
In a preferred aspect of the invention, the fresh air can be injected into the fresh air section at an angle of between +/−60° to a flow axis by way of the nozzle, which leads to a desired positive increase in turbulence. Advantageously, the nozzle may be a separate component and be made of metal or a plastic. The nozzle may be machined directly into a gas exchange inlet duct wall. The fresh gas line can be fed with fresh air by a pressure accumulator or a compressor or a feed point in the fresh air section ahead of the throttle element in the flow direction of the fresh air.
In a further embodiment, a vortex tube is arranged in the fresh gas line. This embodiment enables setting of a cooling ratio of the fresh air in the fresh air section in a simple manner. This leads to a better filling ratio of the cylinders and thus advantageously to an increase in the power of the combustion engine without additional measures.
An Otto-cycle combustion engine having a fresh gas line with a nozzle according to the invention arranged close to the gas exchange inlet valve and operating on the Bernoulli, Venturi or Coanda effect to increase charge movement receives its fresh air mass flow from a pressure accumulator or a compressor, for example. The accumulator or compressor has the task, on the one hand, of ensuring the required air mass to deflect the main air mass flow in the fresh air section ahead of the gas exchange inlet valve and hence to maximize charge movement, it being possible, on the other hand, for this fresh air mass flow to be passed through a vortex tube, which cools the injected air mass by up to 46° C. under ambient conditions, depending on the operating parameters set. This cold fresh air mass cools the main air mass flow in the fresh air section ahead of the gas exchange inlet valve in accordance with the overall configuration (air mass distribution of main air mass flow/fresh air mass flow, ambient temperature, prevailing pressure conditions and vortex tube specifications) and, by means of the cooler combustion air, advantageously ensures higher power from the Otto-cycle combustion engine, in addition to the advantages of better mixture formation (charge movement in the cylinder).
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.